Unified polarizing plate and method for preparing the same

ABSTRACT

The present invention relates to a unified polarizing plate, which employs, as a protection layer of a polarizing film, a transparent film that can simultaneously function as a negative C-plate and transparent protection layer of a polarizing film and has negative refractive index toward thickness direction, thereby simultaneously performing functions as a negative C-plate for optical compensation and as a polarizing plate, and a method for preparing the same. The unified polarizing plate has superior durability at high temperature and high humidity compared to those employing TAC as a protection layer, and improves wide view angle of liquid crystal display having positive refractive index toward thickness direction, when the liquid crystal display device is ON or OFF.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a unified polarizing plate thatsimultaneously functions as a negative C-plate and a polarizing plate,and a method for preparing the same.

(b) Description of the Related Art

The present invention relates to a polarizing plate comprising atransparent protection layer, a polarizing film and a transparentprotection layer, in which at least one of the transparent protectionlayer has negative refractive index toward thickness direction. Moreparticularly, the present invention relates to a unified polarizingplate capable of simultaneously functioning as a negative C-plate and asa polarizing plate, and a method for preparing the same.

Recently, liquid crystal display shows a tendency to increase its areafrom small size mobile phone, notebook monitor to middle to large sizedisplay device of computer monitor and television. Particularly, in thecase of middle to large size liquid crystal display, it is important tohave clear definition at wide view angle and improve luminosity contrastat ON/OFF of the operation cell, for securing quality of competitivedisplay.

For such reasons, displays of various liquid crystal cell modes, such asDual Domain TN, ASM (Axially symmetric aligned microcell), VA (verticalalignment), SE (surrounding electrode), PVA (Patterned VA), IPS(In-Plane Switching) mode, and the like, are under development. Thesemodes respectively have unique liquid crystal alignment and have uniqueoptical anisotropy. Thus, in order to compensate change in optical axisof linearly polarized light due to optical anisotropy of these liquidcrystal modes, compensation films of various optical anisotropies arerequired.

In order for optical compensation of liquid crystal displays of variousmodes, it is important to develop an optical film that can controloptical anisotropy precisely and effectively. An optical anisotropy isdivided into R_(e), an in-plane phase difference value, and R_(th), aphase difference value of in-plane fast axis (y-axis) and towardthickness direction (z-axis), as shown in the following equations 1 and2.R _(th)=Δ(n _(y) −n _(z))×d  [Equation 1]R _(e)=Δ(n _(x) −n _(y))×d  [Equation 2]

-   -   wherein, n_(x) is refractive index of in-plane slow axis        (x-axis), n_(y) is refractive index of in-plane fast axis        (y-axis), and n_(z) is refractive index toward thickness        direction (z-axis), and d is thickness of a film.

In case one of R_(e) or R_(th) calculated by the above equations aremuch larger than the other, the film can be used as a compensation filmhaving uniaxial optical anisotropy, and in case both are larger than 0and similar to each other, the film can be used as a compensation filmhaving biaxial optical anisotropy.

As the compensation film having uniaxial optical anisotropy, A-plate(n_(x)≠n_(y)≅n_(z)) and C-plate (n_(x)≅n_(y)≠n_(z)) can be exemplified.Considering compensation of optical axis polarized due to liquid crystalonly, an ideal compensation film should have an optical axis that ismirror image of the optical axis of liquid crystal layer, and thus, inthe case of liquid crystal display of VA mode or TN mode oriented suchthat refractive index toward thickness direction is larger than thattoward in-plane direction, a negative C-plate having negativebirefringence toward thickness direction is required.

Since the negative C-plate has very small R_(e) value, R_(th) can becalculated from the following equation 3 by measuring R_(θ), which isthe product of the length of light progress route and refractive indexdifference

(n_(y)−n_(θ)) (wherein n_(y) is refractive index of fast axis and θ isan angle between normal to the surface of a film and incident light).$\begin{matrix}{R_{th} = \frac{R_{\theta} \times \cos\quad\theta_{f}}{\sin^{2}\quad\theta_{f}}} & \left\lbrack {{Equation}\quad 3} \right\rbrack\end{matrix}$

-   -   wherein, θ_(f) is internal angle.

As a polymer material that can be used as such negative C-plate,discotic liquid crystal (U.S. Pat. No. 5,583,679) and polyimide havingplanar phenyl group in the main chain (U.S. Pat. No. 5,344,916), etchave been reported.

Since these materials have too large birefringence toward thicknessdirection and show light absorption at a visible ray, they cannotrealize thickness of 30 to 150 μm that is suitable for a protectionlayer of a polarizing film. Thus, in case these materials are used for aprotection layer of a polarizing film, precision coating thereof on atransparent protection layer is needed, which increases cost duringcoating process and causes non-uniformity of large phase difference evenby slight difference in coating thickness due to comparatively largebirefringence. Additionally, there is a problem of optical defect due toforeign substance such as dust remaining on the surface of coating filmor existing in coating solution. Also, since materials comprising thesearomatic compounds have large phase difference change rate according towavelength, in case they are used for a protection film, compensationfor wavelength dispersion due to them should also be considered.

Conventional polarizing plate consists of a polarizing film made ofpolyvinyl alcohol (PVA) and triacetate cellulose (TAC) protection layerthat protects the polarizing film on both sides of the PVA polarizingfilm. Such polarizing plate is prepared by coating organic material suchas discotic liquid crystal having negative birefringence towardthickness direction on a protection layer of the polarizing plate, or bylaminating one or more films having slight birefringence towardthickness direction on a protection layer using an adhesive, in orderfor optical compensation toward thickness direction. Thus, itsproduction process is complicated and is not favorable in terms ofeconomy.

Additionally, although conventional TAC (triacetate cellulose)protection layer of polarizing plate has superior protectionperformance, it shows comparatively high moisture absorption, and thusthere are problems of deterioration in polarizing degree and lightleakage under high temperature high humidity conditions, and inferiordurability.

Meanwhile, cyclic olefin copolymers are well known through literatures,and they have low dielectric constant due to high hydrocarbon content,and low hygroscopic property, are amorphous, and do not have lightabsorption at visible ray area due to π-conjugation, and thus haveexcellent light permeability. The cyclic monomers can be polymerized byROMP (ring opening metathesis polymerization), HROMP (ring openingmetathesis polymerization followed by hydrogenation), copolymerizationwith ethylene and homopolymerization, and the like, as shown in thefollowing Reaction Formula 1. Wherein, in case the same kinds ofmonomers are polymerized using different polymerization methods,polymers having different structure are obtained, and their physicalproperties differ from each other.

Cyclic olefin-based addition polymers obtained by additionpolymerization using homogeneous catalyst, unlike polymers obtained byROMP or copolymerization with ethylene, have rigid and bulky ringstructure in three-dimensions in every monomer unit of the main chain.Thus, the conformational properties of polymer chains differ from thoseof polymers prepared by ROMP or copolymerization with ethylene, and theyare amorphous polymers having comparatively higher glass transitiontemperature. Particularly, norbornene-based polymers havingcomparatively large molecular weight obtained by addition polymerizationusing an organic metal compound as a catalyst are mostly polymers ofnon-polar alkyl norbornene or copolymers with olefin, or comprisetri-ethoxy silyl norbornene having weak polarity as monomers, and theyhave low dielectric constant and excellent electrical anisotropy (J.Appl. Polym. Sci. Vol 80, p 2328, 2001).

Introduction of substituent groups into a polymer consisting ofhydrocarbon is useful for controlling chemical and physical propertiesof polymer. However, since free electron pair at such substituent groupoften reacts with activated catalyst site to act as a poison of acatalyst, it is not easy to introduce substituent group into a polymer.In case cyclic monomers having substituent groups are polymerized, theobtained polymer has low molecular weight. Generally, norbornene-basedpolymers are polymerized using transition organic metal catalyst, mostof which show low activity for polymerizing monomers comprising polargroups such as ester or acetate group, and the produced polymer has amolecular weight of 10,000 or less (Risse et al., Macromolecules, 1996,Vol. 29, 2755-2763; Risse et al., Makromol. Chem. 1992, Vol. 193,2915-2927; Sen et al., Organometallics 2001, Vol 20, 2802-2812, Goodallet al., U.S. Pat. No. 5,705,503).

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a unified polarizingplate simultaneously performing functions as a negative C-plate foroptical compensation and as a polarizing plate, employing apolynorbornene based transparent film having negative birefringencetoward thickness direction that can simultaneously function as anegative C-plate and as a transparent protection film of polarizingfilm.

It is another object of the present invention to provide a unifiedpolarizing plate wherein on at least one side of a polarizing film, atransparent film comprising cyclic olefin-based addition polymer thathas negative birefringence toward thickness direction and shows littlechange in birefringence according to wavelength is laminated as anoptical compensation/protection film, and a method for preparing thesame. The “optical compensation/protection film” herein means a filmthat is employed for a protection film of a polarizing film, and hasR_(th) of 60˜1000 nm at a thickness of 30˜200 μm, within which range thefilm has negative birefringence, and more preferably, R_(th) of 100˜600nm at a thickness of 50˜150 μm.

It is still another object of the present invention to provide unifiedpolarizing plate employing as a protection layer of a polarizing film, atransparent film that can control birefringence toward thicknessdirection by controlling the kinds and contents of functional groupsintroduced into cyclic olefin monomer, and a method for preparing thesame.

It is still another object of the present invention to provide apolarizing plate employing as a protection layer of a polarizing film atransparent film that comprises cyclic olefin-based addition polymer andhas excellent absorption resistance, and a method for preparing thesame.

It is still another object of the present invention to provide a liquidcrystal display comprising a unified polarizing plate comprising acompensation/protection film comprising cyclic olefin-based additionpolymer having negative birefringence toward thickness direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order to achieve these objects, the present invention provide apolarizing plate comprising

-   -   a) a polarizing film; and    -   b) a protection layer of a transparent film comprising cyclic        olefin-based addition polymer.

The present invention also provides a unified polarizing plate whereinon at least one side of a polarizing film, an optically anisotropictransparent film, which has retardation value (R_(th)) of 60 to 1000 nm,calculated by the following equation 1, and has phase difference ratio(R₄₅₀/R₅₅₀) of 1 to 1.05 and phase difference ratio (R₆₅₀/R₅₅₀) of 0.95to 1, is laminated (wherein R₄₅₀ is phase difference at a wavelength of450 nm, and R₅₅₀ is phase difference at a wavelength of 550 nm, and R₆₅₀is phase difference at a wavelength of 650 nm):R _(th)=Δ(n _(y) −n _(z))×d  [Equation 1]

-   -   wherein    -   n_(y) is refractive index of in-plane fast axis, measured at a        wavelength of 550 nm,    -   n_(z) is refractive index toward thickness direction, measured        at a wavelength of 550 nm, and    -   d is a thickness of a film.

The present invention also provides a method for preparing a polarizingplate having negative refractive index toward thickness direction,comprising the steps of:

-   -   a) conducting addition polymerization of norbornene-based        monomers to prepare norbornene addition polymer;    -   b) dissolving the norbornen-based addition polymer in a solvent-        to prepare norbornen-based addition polymer solution;    -   c) coating or casting the norbornen-based addition polymer        solution on a hard surface and drying; and    -   d) laminating the cast film on a polarizing film.

The present invention also provides a liquid crystal display comprisinga unified polarizing plate comprising a negative C-plate type opticallyanisotropic film comprising cyclic olefin-based addition polymer as aprotection layer.

The present invention will now be explained in more detail.

The inventors have discovered that a conformational unit of cyclicolefin is rigid and bulky and thus constitutes an extended conformation,thereby having anisotropy in single molecule, and that if a polar groupis introduced into norbornene-based polymer having such extendedconformation, intermolecular interaction increases compared to polymershaving compact conformation, thereby having directional order tointermolecular packing, and having optical and electric anisotropy.Also, they have discovered that a film comprising the cyclic olefinaddition polymer has phase difference R_(th) toward thickness of 60˜1000nm at a thickness of 30 to 200 μm, within which range a film can be usedas a protection layer of a polarizing film, and more preferably R_(th)of 100˜600 nm at a wavelength of 50 to 150 μm, and it shows littlechange according to wavelength, and that such a film having negativebirefringence toward thickness has low moisture absorption and superioradhesion to PVA, and thus when employed as a protection layer of apolarizing film, it offers superior durability.

In order for optical compensation toward thickness direction, thepresent invention provides a unified polarizing plate employing as aprotection layer a cyclic olefin-based compensation/protection filmhaving negative birefringence toward thickness direction on at least oneside of a polarizing film. The unified polarizing plate is differentfrom conventional polarizing plate comprising a protection film,polarizing film, and another protection film. To compensate the lightleakage at wide view angle of a liquid crystal display device which hasa positive birefringence when the power is ON or OFF, the conventionalpolarizing plate needs additional articles like an organic substancecoating layer such as discotic liquid crystal having negativebirefringence toward thickness direction, or one or more stretched orunstretched films having slight negative birefringence toward thicknessdirection which can be laminated on a protection layer employing anadhesive. However, unified polarizing plate does not need additionalarticle of negative C-plate for compensation at wide view angle, sincethe cyclic olefin based compensation/protection film has a relativelyhigh negative retardation value toward thickness direction.

The “compensation/protection film” herein means a film that can be usedas a negative C-plate with a thickness of 30 to 200 μm, preferably 50 to150 μm, having negative birefringence toward thickness direction, as aprotection layer of a PVA polarizing film, and the “unified polarizingplate” means a polarizing plate wherein the compensation/protection filmis laminated on at least one side of a PVA polarizing film.

For this, the present invention provides a unified polarizing plateemploying an anisotropic film of a negative C-plate type as a protectionlayer. Particularly, the present invention provides a unified polarizingplate employing a film comprising cyclic olefin addition polymer that isobtained by addition polymerization of norbornene-based monomers, on atleast one side of a polarizing film as a protection layer, and a methodfor preparing the same, and a liquid crystal display comprising thesame.

The cyclic olefin-based addition polymer prepared by additionpolymerization of norbornene-based monomers includes polymers preparedby addition polymerization of monomers of the following Chemical Formula1 alone or in combination of two or more kinds:

-   -   wherein,    -   m is an integer of 0 to 4,    -   R₁, R₂, R₃, and R₄ are independently or simultaneously, a        hydrogen; halogen; straight or branched alkyl, alkenyl or vinyl        having 1 to 20 carbon atoms; cycloalkyl having 4 to 12 carbon        atoms, substituted or unsubstituted with hydrocarbon; aryl        having 6 to 40 carbon atoms, substituted or unsubstituted with        hydrocarbon; aralkyl having 7 to 15 carbon atoms, substituted or        unsubstituted with hydrocarbon; alkynyl having 3 to 20 carbon        atoms; or    -   a polar functional group selected from the group consisting of        straight or branched haloalkyl, haloalkenyl or halovinyl having        1 to 20 carbon atoms; halocycloalkyl having 4 to 12 carbon        atoms, substituted or unsubstituted with hydrocarbon; haloaryl        having 6 to 40 carbon atoms, substituted or unsubstituted with        hydrocarbon; haloaralkyl having 7 to 15 carbon atoms,        substituted or unsubstituted with hydrocarbon; haloalkynyl        having 3 to 20 carbon atoms; and non-hydrocarbonaceous polar        group comprising at least one of oxygen, nitrogen, phosphor,        sulfur, silicon, or boron,    -   when R₁, R₂, R₃ and R₄ are not hydrogen, halogen or polar        functional group, R₁ and R₂ or R₃ and R₄ may be connected with        each other to form an alkylidene group having 1 to 10 carbon        atoms, or R₁ or R₂ may be connected with one of R₃ and R₄ to        form a saturated or unsaturated cyclic group having 4 to 12        carbon atoms, or aromatic cyclic compound having 6 to 24 carbon        atoms.

The non-hydrocarbonaceous polar group of the above Chemical Formula 1 ispreferably selected from the group consisting of:

-   -   —C(O)OR₆, —R₅C(O)OR₆, —OR₆, —R₅OR₆, —OC(O)OR6, —R₅OC(O)OR₆,        —C(O)R₆, —R₅C(O)R₆, —OC(O)R₆, —R₅OC(O)R₆, —(R₅₀)_(p)—OR₆,        —(OR₅)_(p)—OR₆, —C(O)—O—C(O)R₆, —R₅C(O)—O—C(O)R₆, —SR₆, —R₅SR₆,        —SSR₆, —R₅SSR₆, —S(═O)R₆, —R₅S(═O)R₆, —R₅C(═S)R₆, —R₅C(═S)SR₆,        —R₅SO₃R₆, —SO₃R₆, —R₅N═C═S, —NCO, R₅—NCO, —CN, —R₅CN,        —NNC(═S)R₆, —R₅NNC(═S)R₆, —NO₂, —R₅NO₂,    -   wherein each R₅ is a straight or branched alkyl, haloalkyl,        alkenyl, haloalkenyl, vinyl, halovinyl having 1 to 20 carbon        atoms; cycloalkyl or halocycloalkyl having 4 to 12 carbon atoms,        substituted or unsubstituted with hydrocarbon; aryl or haloaryl        having 6 to 40 carbon atoms, substituted or unsubstituted with        hydrocarbon; aralkyl or haloaralkyl having 7 to 15 carbon atoms,        substituted or unsubstituted with hydrocarbon; or, alkynyl or        haloalkynyl having 3 to 20 carbon atoms,    -   each of R₆, R₇ and R₈ is a hydrogen; halogen; straight or        branched alkyl, haloalkyl, alkenyl, haloalkenyl, vinyl,        halovinyl, alkoxy, haloalkoxy, carbonyloxy, halocarbonyloxy        having 1 to 20 carbon atoms; cycloalkyl or halocycoalkyl having        4 to 12 carbon atoms, substituted or unsubstituted with        hydrocarbon; aryl, haloaryl, aryloxy, or haloaryloxy having 6 to        40 carbon atoms, substituted or unsubstituted with hydrocarbon;        aralkyl or haloaralkyl having 7 to 15 carbon atoms, substituted        or unsubstituted with hydrocarbon; alkynyl or haloalkynyl having        3 to 20 carbon atoms, and    -   p is an integer of 1 to 10.

The “norbornene-based monomer” herein means a monomer comprising atleast one norbornene(bicyclo[2,2,1]hept-2-ene) unit of the followingChemical Formula 2.

As the norbornene-based addition polymer, which is a material of theoptically anisotropic film of negative C-plate type of the presentinvention, any cyclic olefin-based polymers prepared by additionpolymerization of norbornene-based monomers can be used, and variouscyclic olefin polymers can be used depending on a catalyst systememployed during addition polymerization. The addition polymers include:a homopolymer of norbornen-based monomers comprising non-polarfunctional group, a copolymer of norbornene-based monomers comprisingdifferent kinds of non-polar functional groups, a homopolymer ofnorbornene-based monomers comprising polar functional group, a copolymerof norbornene-based monomers comprising different kinds of polarfunctional groups, and a copolymer of norbornene-based monomerscomprising non-polar functional group and norbornene-based monomerscomprising polar functional group. It is preferable to usenorbornene-based polymer having polar group with a number averagemolecular weight of 10,000 or more. The addition polymerization iscarried out by a common polymerization method, by mixing monomers to bepolymerized and a catalyst in a solvent.

The polar groups introduced into the cyclic olefin-based additionpolymer, although they can be chosen depending on a specific catalystsystem, are not specifically limited. And, polymer capable ofcontrolling optical anisotropy can be prepared while the kinds andcontents of the polar functional group or non-polar functional group arevaried, and such a polymer can be used as a compensation/protection filmthat can be used for optical compensation toward thickness direction ofLCD and as a protection layer of a PVA polarizing film.

The cyclic olefin-based addition polymer into which the polar group isintroduced can be prepared by various methods, and preferably preparedby addition polymerization of norbornene-based monomers in the presenceof Group 10 transition metal catalyst.

More preferably, a cyclic olefin-based polymer into which a polar groupis introduced is prepared with high yield and high molecular weight, bya method comprising the step of contacting the norbornene-based monomersof the above Chemical Formula 1 with a catalyst component of a catalystsystem which comprises a catalyst component of Group 10 transition metalcompound, a cocatalyst component of an organic compound that comprisesGroup 15 element and has noncovalent electron pair capable offunctioning as an electron donor, and a cocatalyst component of a saltcomprising Group 13 element capable of offering an anion that can beweakly coordinated to the transition metal, thereby effecting anaddition polymerization.

Additionally, a cyclic olefin-based polymer comprising a polar group ofester or acetyl group is preferably prepared by a method comprisingcontacting norbornene-based monomers comprising a polar group of esteror acetyl group selected from the norbornene-based monomers of the aboveChemical Formula 1 with a catalyst component of a catalyst system whichcomprises

-   -   i) Group 10 transition metal compound;    -   ii) a compound having a cone angle of at least 160° and        comprising neutral Group 15 electron donor ligand; and    -   iii) a salt capable of offering an anion that can be weakly        coordinated to the i) transition metal. However, a cyclic        olefin-based polymer comprising a polar group and its        preparation method are not limited to the above.

The i) Group 10 transition metal is preferably a compound represented bythe following Chemical Formula 3, or a compound represented by thefollowing Chemical Formula 4:M(R)(R′)  [Chemical Formula 3]

-   -   wherein,    -   M is Group 10 metal,    -   R and R′ are leaving groups of an anion that can be easily left        by a weakly coordinating anion, and are selected from the group        consisting of hydrocarbyl, halogen, nitrate, acetate,        trifluoromethanesulfonate, bistrifluoromethanesulfonimide,        tosylate, carboxylate, acetylacetonate, carbonate, aluminate,        borate, antimonite such as SbF₆—, arsenate such as AsF₆—,        phosphate such as PF₆— or PO₄—, perchlorate such as ClO₄—, amide        such as (R″)₂N, and phosphide such as (R″)₂P,    -   Wherein the hydrocarbyl anion is selected from the group        consisting of: hydride; straight or branched alkyl, haloalkyl,        alkenyl, haloalkenyl, vinyl or halovinyl having 1 to 20 carbon        atoms; cycloalkyl or halocycloalkyl having 4 to 12 carbon atoms,        substituted or unsubstituted with hydrocarbon; aryl or haloaryl        having 6 to 40 carbon atoms, substituted or unsubstituted with        hydrocarbon; aryl or haloaryl having 6 to 40 carbon atoms        comprising hetero atom; aralkyl or haloaralkyl having 7 to 15        carbon atoms, substituted or unsubstituted with hydrocarbon; and        alkynyl or haoalkynyl having 3 to 20 carbon atoms,    -   the acetate anion is an anion ligand offering σ bond such as        [R″C(O)O]⁻ and the acetylacetonate anion is an anion ligand        offering π bond such as [R″C(O)CHC(O)R″″]⁻, and    -   R″, R′″ and R″″ are respectively a hydrogen; halogen; straight        or branched alkyl, haloalkyl, alkenyl, haloalkenyl, vinyl or        halovinyl having 1 to 20 carbon atoms; cycloalkyl or        halocycloalkyl having 4 to 12 carbon atoms, substituted or        unsubstituted with hydrocarbon; aryl or haloaryl having 6 to 40        carbon atoms, substituted or unsubstituted with hydrocarbon;        aryl or haloaryl having 6 to 40 carbon atoms comprising hetero        atom; aralkyl or haloaralkyl having 7 to 15 carbon atoms,        substituted or unsubstituted with hydrocarbon; or alkynyl or        haloalkynyl having 3 to 20 carbon atoms.

The ii) compound having a cone angle of at least 160° and comprisingneutral Group 15 electron donor ligand is preferably a compoundrepresented by the following Chemical Formula 5 or a compoundrepresented by the following Chemical Formula 6.P(R⁵)_(3-c)[X(R⁵)_(d)]_(c)  [Chemical Formula 5]

-   -   Wherein,    -   X is an oxygen, a sulfur, a silicon, or a nitrogen;    -   c is an integer of 0 to 3; when X is an oxygen or a sulfur, d is        1, when X is a silicon, d is 3, and when X is a nitrogen, d is        2;    -   when c is 3 and X is an oxygen, 2 or 3 R⁵s may be connected each        other together with an oxygen to form a cyclic group; and, when        c is 0, 2 R⁵s may be connected each other to form a        phosphacycle;    -   R⁵ is a hydrogen; straight or branched alkyl, alkoxy, allyl,        alkenyl or vinyl having 1 to 20 carbon atoms; cycloalkyl having        4 to 12 carbon atoms, substituted or unsubstituted with        hydrocarbon; aryl having 6 to 40 carbon atoms, substituted or        unsubstituted with hydrocarbon; aralkyl having 7 to 15 carbon        atoms, substituted or unsubstituted with hydrocarbon; alkynyl        having 3 to 20 carbon atoms; tri(C1-10 linear or branched        alkyl)silyl, tri(C1-10 linear or branched alkoxy)silyl;        tri(C5-12 cycloalkyl substituted or unsubstituted with        hydrocarbon)silyl; tri(C6-40 aryl substituted or unsubstituted        with hydrocarbon)silyl; tri(C6-40 aryloxy substituted or        unsubstituted with hydrocarbon)silyl; tri(C1-10 linear or        branched alkyl)silyl; tri(C4-12 cycloalkyl substituted or        unsubstituted with hydrocarbon); or tri(C6-40 aryl substituted        or unsubstituted with hydrocarbon), each of which may be        substituted with linear or branched haloalkyl or halogen,        (R⁵)₂P—(R⁶)—P(R⁵)₂  [Chemical Formula 6]    -   wherein    -   R⁵ is as defined in the Chemical Formula 5,    -   R⁶ is linear or branched alkyl, alkenyl or vinyl having 1 to 5        carbon atoms; cycloalkyl having 4 to 12 carbon atoms,        substituted or unsubstituted with hydrocarbon; aryl having 6 to        20 carbon atoms, substituted or unsubstituted with hydrocarbon;        or aralkyl having 7 to 15 carbon atoms, substituted or        unsubstituted with hydrocarbon.

The iii) salt capable of offering an anion that can be weaklycoordinated to the i) transition metal is preferably represented by thefollowing Chemical Formula 7:[Cat]_(a)[Anion]_(b)  [Chemical Formula 7]

-   -   wherein    -   Cat is a hydrogen; a cation of Group I metal, Group II metal, or        transition metal; or a cation selected from organic groups        comprising these cations, to which the ii) weakly coordinating        neutral Group XV electron donor compound can be bonded;    -   Anion is an anion that can be weakly coordinated to the metal M        of the compound of the above Chemical Formula 3, and is selected        from the group consisting of borate, aluminate, SbF₆₋, PF₆₋,        AlF₃O₃SCF₃₋, SbF₅SO₃F₋, AsF₆₋, perfluoroacetate (CF₃CO₂₋),        perfluoropropionate (C₂F₅CO₂₋), perfluorobutyrate        (CF₃CF₂CF₂CO₂₋), perchlorate (ClO₄₋), para-toluenesulfonate        (p-CH₃C₆H₄SO₃₋), SO₃CH₃₋, boratabenzene, and carborane        substituted or unsubstituted with halogen;    -   a and b respectively indicate the number of cations and anions,        and these are determined so as to be electrically neutral.

The organic group comprising the cation of the Chemical Formula 7 ispreferably selected from the group consisting of ammonium such as[NH(R⁷)₃]⁺, or [N(R⁷)₄]⁺; phosphonium such as [PH(R⁷)₃]⁺, or [P(R⁷)₄]⁺;carbonium such as [C(R⁷)₃]⁺; silylium such as [Si(R⁷)₃]⁺; [Ag]⁺;[Cp₂Fe]⁺; and [H(OEt₂)₂]⁺. Wherein, R7 is linear or branched alkyl,alkyl substituted with halogen, or silyl alkyl, each having 1 to 20carbon atoms; cycloalkyl having 4 to 12 carbon atoms substituted orunsubstituted with hydrocarbon; cycloalkyl or silyl cycloalkylsubstituted with halogen; aryl having 6 to 40 carbon atoms, substitutedor unsubstituted with hydrocarbon; aralkyl having 7 to 15 carbon atoms,substituted or unsubstituted with hydrocarbon; or aralkyl or silylaralkyl substituted or unsubstituted with halogen.

The borate or aluminate of the Chemical Formula 3, 4 and 7 is preferablyan anion represented by the following Chemical Formula 8 or 9:[M′(R⁸)(R⁹)(R¹⁰)(R¹¹)]  [Chemical Formula 8][M′(OR¹²)(OR¹³)(OR¹⁴)(OR¹⁵)]  [Chemical Formula 9]

-   -   wherein, M′ is boron or aluminum,    -   R⁸, R⁹, R¹⁰, R¹¹, R¹², R¹³, R¹⁴, and R¹⁵ are halogen; linear or        branched alkyl or alkenyl having 1 to 20 carbon atoms,        substituted or unsubstituted with halogen; cycloalkyl having 4        to 12 carbon atoms, substituted or unsubstituted with        hydrocarbon; aryl having 6 to 40 carbon atoms, substituted or        unsubstituted with hydrocarbon; aralkyl having 7 to 15 carbon        atoms, substituted or unsubstituted with hydrocarbon; linear or        branched trialkylsiloxy having 3 to 20 carbon atoms; or linear        or branched triarylsiloxy having 18 to 48 carbon atoms.

The catalyst system can avoid decrease in catalyst activity due to esteror acetyl group of endo-isomer by introducing suitable ligand and thushas high activity, and it enables easy preparation of cyclicolefin-based addition polymer comprising a polar group of ester oracetyl group.

The cyclic olefin-based addition polymer used for preparing thecompensation/protection film of negative C-plate of a unified polarizingfilm of the present invention does not show light loss due to lightabsorption in visible light region, shows comparatively low moistureabsorption, and if a polar functional group is introduced, it has highersurface tension compared to the case where only non-polar functionalgroups exist, and it also has excellent adhesion to polyvinylalcohol(PVA) film.

The optical anisotropic film of the present invention, in order toincrease negative birefringence toward thickness direction, preferablyintroduces ester or acetyl group into norbornene-based monomers of theChemical Formula 1, and other functional groups including alkoxy, amino,hydroxyl and carbonyl group, and halogen atom can also be introduced.However, the functional groups are not limited to the above. As shown inthe following Examples, refractive index and R_(th) value can becontrolled by varying the kinds and contents of the substituent groupsintroduced into norbornene.

Generally, in order to obtain high R_(th), a cyclic olefin having largem in the above Chemical Formula 1 is introduced, the contents of polarfunctional groups increase, the length of the substituent groupdecreases by decreasing the number of carbons existing in R₁, R₂, R₃, R₄and R₅, which determines the length of the substituent group ofnorbornene-based monomer, a functional group having high polarity isintroduced, or, a cyclic olefin wherein R₁ or R₂ is connected to one ofR₃ and R₄ to form an aromatic cyclic compound having 6 to 24 carbonatoms.

The compensation/protection film of negative C-plate employed in theunified polarizing plate of the present invention is prepared in theform of film or sheet by dissolving the above-explained cyclicolefin-based addition polymer in a solvent and carrying out solutioncasting.

The film is prepared from a homopolymer of norbornene-based monomerscomprising non-polar functional group, a copolymer of norbornene-basedmonomers comprising different kinds of non-polar functional group, ahomopolymer of norbornene-based monomers comprising a polar functionalgroup, a copolymer of norbornene-based monomers comprising differentkinds of polar functional groups, or a copolymer of norbornen-basedmonomers comprising non-polar functional group and norbornene-basedmonomers comprising polar functional group. And, the film can also beprepared from a blend of one or more kinds of the cyclic olefinpolymers.

As the organic solvent employed for solution casting, those whichdissolve cyclic olefin-based addition polymer and show appropriateviscosity are preferred, and more preferably, ether having 3 to 12carbon atoms, ketone having 3 to 12 carbon atoms, ester having 3 to 12carbon atoms, halogenated hydrocarbon having 1 to 6 carbon atoms,aromatic compounds, or the mixture thereof is selected. The ether,ketone and ester compound may have ring structure. And, compounds having2 or more ether, ketone or ester functional group can be used, andcompounds having one or more functional groups together with halogenatom can also be used.

The examples of the ether having 3 to 12 carbon atoms includediisopropylether, dimethoxymethane, tetrahydrofuran, and the like, andthe examples of the ester having 3 to 12 carbon atoms include ethylformate, propyl formate, pentyl formate, methyl acetate, ethyl acetate,propyl acetate, isopropyl acetate, isobutyl acetate, pentyl acetate andthe like. The halogenated hydrocarbon preferably has 1 to 4 carbonatoms, more preferably one carbon atoms, the preferred halogen atoms ischlorine, and its representative examples include methylene chloride.The examples of aromatic compounds include benzene, toluene andchlorobenzene, and the like.

In order to prepare a film by solution casting, it is preferable tointroduce cyclic olefin-based addition polymer in a solvent in an amountof 5 to 95 wt %, more preferably 10 to 60 wt %, and stirring the mixtureat room temperature. The viscosity of the prepared solution ispreferably 100 to 50000 cps, more preferably 500 to 20000 cps forsolution casting. In order to improve mechanical strength, heatresistance, light resistance, and manipulability of the film, additivessuch as plasticizer, anti-deterioration agent, UV stabilizer andantistatic agent can be added.

As the plasticizer, carboxylic ester or phosphate ester can be used. Theexamples of the carboxylic ester include dimethyl phthalate (DMP),diethylphthalate (DEP), dibutylphthalate (DBP), dioctyl phthalate (DOP),diphenylphthalate (DPP), diethylhexyl phthalate (DEHP), and the like,and the example of the phosphate ester include triphenyl phosphate(TPP), tricresyl phosphate (TCP), and the like. If the contents of thelower molecular plasticizer are excessive, durability of the film maydeteriorate due to diffusion on the film surface, and thus suitablecontents, for example, 0.1 to 20 wt % are preferable. And, it ispreferable to increase the content of the plasticizer as the glasstransition temperature of the cyclic olefin-based addition polymerincreases.

As the anti-deterioration agent, phenol derivatives or aromatic amine ispreferable, and the contents are determined within the range that doesnot deteriorate optical and mechanical properties, and durability of thefilm.

The examples of the phenol-based anti-deterioration agent includeoctadecyl-3-(4-hydroxy-3,5-di-tert-butylphenyl)propionate (Ciga-GeigyCompany, Irganox 1076),tetrabis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane(Ciba-Geigy Company, Irganox 1010),1,3,5-trimethyl-2,4,6-tris-(3,5-di-t-butyl-4-hydroxybenzyl)benzene(Ciba-Geigy Company, Irganox 1330),tris-(3,5-di-t-butyl-4-hydroxybenzyl)isoamine (Ciba-Geigy Company,Irganox 3114), and the like.

The examples of the aromatic amine type anti-deterioration agent includephenyl-α-naphtylamine, phenyl-β-naphtylamine,N,N′-diphenyl-p-phenylenediamine, N,N′-di-β-naphtyl-p-phenylenediamine,and the like.

The anti-deterioration agent can be used together with peroxidedisintegrating agent of phosphite or sulfide compound. The examples ofthe phosphite type peroxide disintegrating agent includetris(2,4-di-t-butylphenyl)phosphite (Ciba-Geigy Company, Irgafos 168)and the like, the examples of the sulfide type disintegrating agentinclude dilauryl sulfide, dilauryl thiodipropionate, distearylthiodipropionate, mercaptobenzothioazole, tetramethylthiurain disulfide,and the like.

As the UV stabilizer, benzophenone, salicylic acid orbenzotriazole-based UV stabilizer is preferred. The examples of thebenzophenone-based UV stabilizer include 2-hydroxy-4-octoxybenzophenone,2,2′-dihydroxy-4,4′-dioctoxy benzophenone and the like, and the examplesof the salicylic acid based UV stabilizer include p-octyl phenylsalicylate and the like, and the examples of the benzotriazole based UVstabilizer include 2-(2′-hydroxy-5′-methylphenyl and the like.

As the antistatic agent, those which can be mixed with polynorbornenesolution can be used, and those having surface specific resistance of10¹⁰ Ω or less are preferred. The examples of the antistatic agentinclude non-ionic, anionic or cationic antistatic agent.

The non-ionic antistatic agent includes polyoxyethylene alkyl ether,polyoxyethylene alkyl phenol ether, polyoxyethylene alkyl ester,polyoxyethylene stearyl amine, polyoxyethylene alkyl amine and the like.

The anionic antistatic agent includes sulfate ester salts, alkyl allylsulfonate salts, aliphatic amide sulfonate salts, phosphate ester saltsand the like.

The cationic antistatic agent includes aliphatic amine salts, alkylpyridinium salts, imidazolin derivatives, betaine type higher alkylamino derivatives, sulfate ester derivatives, phosphate esterderivatives and the like.

Additionally, ionic polymers can also be used, and as examples, anionicpolymer compounds disclosed in Japanese Laid-Open Patent Publication No.49-23828, ionene type compounds having dissociation groups in a ringdisclosed in Japanese Laid-Open Patent Publication No. 55-734, JapaneseLaid-Open Patent Publication No. 59-14735 and Japanese Laid-Open PatentPublication No. 57-18175, cationic polymer compounds disclosed inJapanese Laid-Open Patent Publication No. 53-13223, and graft copolymerdisclosed in Japanese Laid-Open Patent Publication No. 5-230161 can beused as an antistatic agent.

The cyclic olefin-based addition polymer solution is casted or coated ona band or drum, or a glass plate that has a polished hard surface, andthe solvent is dried to obtain an optical film or sheet. Temperature fordrying the solvent can be selected depending on the kinds of theemployed solvent. The metal or glass substrate that has a polished hardsurface has preferably surface temperature of room temperature or less.After sufficiently drying the solvent, the formed film or sheet isexfoliated from the metal (steel) or glass.

The prepared optical film of cyclic olefin-based addition polymer of thepresent invention is an optical anisotropic transparent film havingretardation value (R_(th)) of 60 to 800 nm, calculated from thefollowing equation 1.R _(th)=Δ(n _(y) −n _(z))×d  [Equation 1]

-   -   wherein,    -   n_(y) is refractive index of in-plane fast axis, measured at a        wavelength of 550 nm,    -   n_(z) is refractive index toward thickness direction (z-axis),        measured at a wavelength of 550 nm, and    -   d is a thickness of a film.

Particularly, when the thickness of the film is set to 30 to 200 μm, thefilm can have R_(th) of 60 to 1000 nm, and when the thickness of thefilm is set to 50 to 150 μn, the film can have R_(th) of 100 to 600 nm.The film has excellent transparency, and thus has light permeability of90% or more at 400 to 800 nm, and shows flat wavelength dispersionproperty in that phase difference ratios at two wavelengths observed ata specific inclination angle of (R₄₅₀/R₅₅₀) and (R₆₅₀/R₅₅₀) respectivelyare 1.05 or less and 0.95 or more. Wherein R₄₅₀ is phase differencevalue at a wavelength of 450 nm, R₅₅₀ is phase difference value at awavelength of 550 nm, and R₆₅₀ is phase difference value at a wavelengthof 650 nm. Such flat wavelength dispersion property can be varied byblending or introduction of functional groups into polymers, ifnecessary. Practically, phase difference ratio at two wavelengths of(R₄₅₀/R₅₅₀) is 1 to 1.05, and (R₆₅₀/R₅₅₀) is 0.95 to 1.

The optical film of cyclic olefin-based addition polymer of the presentinvention has excellent adhesion property while having opticalanisotropy, and thus can be adhered to polyvinylalcohol (PVA) polarizingfilm. And, if necessary, before adhesion of the film, a surfacetreatment selected from the group consisting of corona discharge, glowdischarge, flame treatment, acid treatment, alkali treatment, UVirradiation, and coating can be conducted on the film.

When the polarizing plate wherein the optical anisotropic film of cyclicolefin-based addition polymer is laminated as a protection layer of apolarizing film is comprised in a liquid crystal display, the displayhas clear definition at wide view angle, luminosity contrast at ON/OFFof the operation cell can be improved, and a liquid crystal display ofliquid crystal mode satisfying n_(x)≅n_(y)<n_(z) (wherein n_(x) isrefractive index of in-plane slow axis, n_(y) is refractive index offast axis, and n_(z) is refractive index toward thickness direction)when power is ON or OFF can be realized.

The polarizing film employed in the present invention is preferablyprepared by dyeing PVA film with iodine or bi-color pigment, but itspreparation method is not specifically limited.

The unified polarizing plate of the present invention can be prepared bylaminating a compensation/protection film prepared from cyclicolefin-based addition polymer having negative birefringence towardthickness direction on at least one side of a polarizing film. As aprotection layer of the other side of the polarizing film, anytransparent optical film comprising a film prepared from cyclicolefin-based addition polymer can be used. Since the lamination of thecyclic olefin-based negative C-plate of the present invention as aprotection layer causes little phase difference, a continuous process ofroll-to-roll lamination can be employed. The lamination to thepolarizing film can be carried out using an adhesive, and the examplesof the adhesive include PVA adhesive aqueous solution,polyurethane-based adhesive, epoxy-based adhesive, styrene-basedadhesive and hot-melt type adhesive.

In case a PVA adhesive is used, the cyclic olefin-basedcompensation/protection film is surface treated (for example, coronadischarge, plasma treatment, ion beam treatment, and the like), andthen, it is coated using a roll coater, bar coater, knife coater orcapillary coater, and before completely dried, compressed under heatingor room temperature using two rolls and thus laminated.

In case a polyurethane-based adhesive is used, it is preferable toemploy aliphatic isocyanate that does not show yellowing due to lightexposure. And, a mono-liquid type or bi-liquid type adhesive for drylamination can also be used, and in case reactivity between isocyanateand hydroxyl group is comparatively low, a solution type adhesivediluted in a solvent such as acetate, ketone, ether or aromatic solventcan be used. The adhesive preferably has low viscosity of 5000 cps orless. And, a styrene-butadiene rubber adhesive, epoxy-based bi-liquidtype adhesive can also be used. These adhesives preferably have superiorstorage stability, and superior light permeability of 90% or more at400˜800 nm. In addition, a film wherein a hot melt type adhesive iscoated on cyclic olefin-based compensation/protection film can belaminated on a polarizing film using a heating-compression roll.

In order to improve adhesion property, a primer layer can be coated onthe surface of cyclic olefin-based compensation/protection film, orcorona discharge, plasma treatment, ion beam treatment and the like canbe carried out on the surface. And, a tackifying agent can also be used,as long as it shows sufficient adhesion property. It is preferable thatthe tackifying agent is sufficiently cured by heat or UV afterdeposition to improve its mechanical property to a level of adhesive,and that the tackifying agent has very large interface adhesion propertysuch that two films between which a tackifying agent is adhered cannotbe exfoliated without destruction of any one film.

As the tackifying agent, natural rubber, synthetic rubber or elastomerhaving superior optical transparency, a vinyl chloridelvinyl acetatecopolymer, polyvinyl alkyl ether, polyacrylate, modified polyolefinresin adhesive, and a curable adhesive having a curing agent such asisocyante added thereto, and the like, can be exemplified.

Additionally, since TAC (triacetate cellulose), which is a widely usedprotection layer for a polarizing film, shows comparatively highmoisture absorption, it causes problems of light leakage at hightemperature and high humidity, deterioration in polarizing degree, andthe like. However, a polarizing plate employing a transparent filmprepared from cyclic olefin-based addition polymer as a protection layerof a polarizing film shows more improvement in light leakage at hightemperature and high humidity, and in deterioration of polarizing degreethan that employing TAC as a protection layer of a polarizing film.

The present invention will be explained in more detail with reference tothe following Examples. However, the Examples are only to illustrate thepresent invention, and the present invention is not limited to them.

EXAMPLES

Preparation 1

(Polymerization of Norbornene Carboxylic Acid Methylester)

Into a polymerization reactor, norbornene carboxylic acid methylester asmonomers and purified toluene were introduced with a weight ratio of1:1.

Into the reactor, based on the monomers, 0.01 mol % of Pd(acac)₂ and0.01 mol % of tricyclohexylphosphine dissolved in toluene as a catalyst,and 0.02 mol % of dimethylanilinium tetrakiss(pentafluorophenyl)boratedissolved in CH₂Cl₂ as a cocatalyst were introduced, and the mixture wasreacted while stirring at 80° C. for 20 hours.

After the reaction, the reactant was introduced into excessive ethanolto obtain white copolymer precipitate. The precipitate was filteredusing a glass funnel and the recovered copolymer was dried at 65° C. for24 hours in a vacuum oven to obtain norbornene carboxylic acidmethylester (PMeNB).

Preparation 2

(Polymerization of Norbornene Carboxylic Acid Butylester)

Into a polymerization reactor, norbornene carboxylic acid butylester asmonomers and purified toluene as a solvent were introduced with a weightratio of 1:1.

Into the reactor, based on monomers, 0.01 mol % of Pd(acac)₂ and 0.01mol % of tricyclohexylphosphine dissolved in toluene as a catalyst, and0.02 mol % of dimethylanilinium tetrakiss(pentafluorophenyl)boratedissolved in CH₂Cl₂ as a cocatalyst were introduced, and the mixture wasreacted while stirring at 80° C. for 20 hours.

After the reaction, the reactant was introduced into excessive ethanolto obtain white copolymer precipitate. The precipitate was filteredusing a glass funnel and the recovered copolymer was dried at 65° C. for24 hours in a vacuum oven to obtain norbornene carboxylic acidbutylester (PBeNB).

Preparation 3

(Copolymerization of Norbornene Carboxylic Acid Butylester-NorborneneCarboxylic Acid Methylester (Norbornene Carboxylic AcidButylester/Norbornene Carboxylic Acid Methylester=7/3)

Into a polymerization reactor, norbornene carboxylic acid methylesterand norbornene carboxylic acid butylester were introduced in a moleratio of 3:7, and purified toluene was introduced in a weight ratio of1:1, on the basis of total monomers.

Into the reactor, based on monomers, 0.01 mol % of Pd(acac)₂ and 0.01mol % of tricyclohexylphosphine dissolved in toluene, and 0.02 mol % ofdimethylanilinium tetrakiss(pentafluorophenyl borate) dissolved inCH₂Cl₂ as a cocatalyst were introduced, and the mixture was reactedwhile stirring at 80° C. for 20 hours.

After the reaction, the reactant was introduced into excessive ethanolto obtain white copolymer precipitate. The precipitate was filtered witha glass funnel, and the recovered copolymer was dried at 65° C. for 24hours in a vacuum oven to obtain norbornene carboxylic acidbutylester-norbornene carboxylic acid methylester copolymer(PBe-7-Me-3-NB).

Preparation 4

(Copolymerization of Norbornene Carboxylic Acid Butylester-NorborneneCarboxylic Acid Methylester (Norbornene Carboxylic AcidButylester/Norbornene Carboxylic Acid Methylester=5/5)

Into a polymerization reactor, norbornene carboxylic acid methylesterand norbornene carboxylic acid butylester were introduced as monomers ina mole ratio of 5:5, and purified toluene was introduced in a weightratio of 1:1, based on total monomers.

Into the reactor, based on monomers, 0.01 mol % of Pd(acac)₂ and 0.01mol % of tricyclohexylphosphine dissolved in toluene as a catalyst, and0.02 mol % of dimethylanilinium tetrakis(pentafluorophenyl)boratedissolved in CH₂Cl₂ as a cocatalyst were introduced, and the mixture wasreacted while stirring at 80° C. for 20 hours.

After the reaction, the reactant was introduced into excessive ethanolto obtain white copolymer precipitate. The precipitate was filtered witha glass funnel, and the recovered copolymer was dried at 65° C. for 24hours in a vaccum oven to obtain norbornene carboxylic acid methylesterbutylester 5:5 copolymer (PBe-5-Me-5-NB).

Preparation 5

(Copolymerization of Norbornene Carboxylic Acid Butylester-NorborneneCarboxylic Acid Methylester (Norbornene Carboxylic AcidButylester/Norbornene Carboxylic Acid Methylester=3/7)

Into a polymerization reactor, norbornene carboxylic acid methylesterand norbornene carboxylic acid butyl ester were introduced in a moleratio of 7:3 as monomers, and purified toluene was introduced in aweight ratio of 1:1, based on total monomers.

Into the reactor, based on monomers, 0.01 mol % of Pd(acac)₂ and 0.01mol % of tricyclohexylphosphine dissolved in toluene as a catalyst, and0.02 mol % of dimethylanilinium tetrakis(pentafluorophenyl)boratedissolved in CH₂Cl₂ was introduced as a cocatalyst, and the mixture wasreacted while stirring at 80° C. for 20 hours.

After reaction, the reactant was introduced into excessive ethanol toobtain white copolymer precipitate. The precipitate was filtered with aglass funnel and the recovered copolymer was dried at 65° C. for 24hours in a vacuum oven to obtain norbornene carboxylic acid butylestermethylester 3:7 copolymer (PBe-3-Me-7-NB).

Preparation 6

(Copolymerization of Norbornene Carboxylic Acid Methylester-ButylNorbornene (Norbornene Carboxylic Acid Methylester/Butyl Norbornene=3/7)

Into a polymerization reactor, norbornene carboxylic acid methylesterand butyl norbornene were introduced in a mole ratio of 3:7 as monomers,and purified toluene was introduced in a weight ratio of 1:1, based ontotal monomers.

Into the reactor, based on monomers, 0.01 mol % of Pd(acac)₂ and 0.01mol % of tricyclohexylphosphine dissolved in toluene as a catalyst, and0.02 mol % of dimethylanilinium tetrakis(pentafluorophenyl)boratedissolved in CH₂Cl₂ was introduced as a cocatalyst, and the mixture wasreacted while stirring at 90° C. for 20 hours.

After reaction, the reactant was introduced into excessive ethanol toobtain white copolymer precipitate. The precipitate was filtered with aglass funnel and the recovered copolymer was dried at 65° C. for 24hours in a vacuum oven to obtain norbornene carboxylic acidmethylester/butyl norbornene 3:7 copolymer (PBu-7-Me-3-NB).

Preparation 7

(Copolymerization of Norbornene Carboxylic Acid Methylester-ButylNorbornene (Norbornene Carboxylic Acid Methylester/Butyl Norbornene=5/5)

Into a polymerization reactor, norbornene carboxylic acid methylesterand butyl norbornene were introduced in a mole ratio of 5:5 as monomers,and purified toluene was introduced in a weight ratio of 1:1, based ontotal monomers.

Into the reactor, based on monomers, 0.01 mol % of Pd(acac)₂ and 0.01mol % of tricyclohexylphosphine dissolved in toluene as a catalyst, and0.02 mol % of dimethylanilinium tetrakis(pentafluorophenyl)boratedissolved in CH₂Cl₂ was introduced as a cocatalyst, and the mixture wasreacted while stirring at 90° C. for 18 hours.

After reaction, the reactant was introduced into excessive ethanol toobtain white copolymer precipitate. The precipitate was filtered with aglass funnel and the recovered copolymer was dried at 65° C. for 24hours in a vacuum oven to obtain norbornene carboxylic acidmethylester/butyl norbornene 5:5 copolymer (PBu-5-Me-5-NB).

Preparation 8

(Polymerization of Acetate Norbornene)

Into a polymerization reactor, acetate norbornene as monomers andpurified toluene were introduced in a weight ratio of 1:1.

Into the reactor, based on monomers, 0.03 mol % of Pd(acac)₂ and 0.03mol % of tricyclohexylphosphine dissolved in toluene as a catalyst, and0.06 mol % of dimethylanilinium tetrakis(pentafluorophenyl)boratedissolved in CH₂Cl₂ as a cocatalsyt were introduced, and the mixture wasreacted while stirring at 80° C. for 17 hours.

After the reaction, the reactant was introduced into excessive ethanolto obtain white copolymer precipitate. The precipitate was filtered witha glass funnel, and the recovered copolymer was dried at 80° C. for 24hours in a vacuum oven to obtain norbornene acetate polymer (PAcNB).

Examples 1˜8

(Preparation of a Film)

Into the norbornene-based addition polymer prepared in Preparations 1 to8, Irganox 1010 (Ciba Company) was introduced in an amount of 0.3 wt %,based on the polymer, as an antioxidant, and methylene chloride wasintroduced as an organic solvent, and a solution with solid content of20 wt % was prepared. The solution was cast on a band using a bandcaster (effective length: 8 m, width: 300 mm), dried, and then,exfoliated from the band to obtain a transparent film with thicknessdeviation within 2%. The film was secondly dried at 100° C. for 4 hours.Then, refractive index (n) was measured using an Abbe refractometer,in-plane phase difference (R_(e)) was measured using an automatic doublerefractometer (Wangja measuring machine; KOBRA-21 ADH), a phasedifference (R_(θ)) was measured when the angle between the incidentlight and normal to the film surface is 50°, and phase difference towardfilm thickness direction (R_(th)) were calculated from the followingequation 3. $\begin{matrix}{R_{th} = \frac{R_{\theta} \times \cos\quad\theta_{f}}{\sin^{2}\quad\theta_{f}}} & \left\lbrack {{Equation}\quad 3} \right\rbrack\end{matrix}$

And, refractive index differences (n_(x)−n_(y)) and (n_(y)−n_(z)) wererespectively calculated by dividing R_(e) and R_(th) by a filmthickness. The thickness of a transparent film and light transmittanceat 400˜800 nm are shown in Table 1, and (n_(x)−n_(y)), R_(θ), R_(th),and (n_(y)−n_(z)) of the transparent film are shown in Table 2. TABLE 1Physical properties of film Light Cyclic transmittance olefin-basedpolymer thickness(μm) (%) Example 1 Polymer of preparation 1, 106 92PMeNB Example 2 Polymer of preparation 2, 125 91 PBeNB Example 3 Polymerof preparation 3, 121 92 PBe-7-Me-3-NB Example 4 Polymer of preparation4, 116 91 PBe-5-Me-5-NB Example 5 Polymer of preparation 5, 102 92PBe-3-Me-7-NB Example 6 Polymer of preparation 6, 101 91 PBu-7-Me-3-NBExample 7 Polymer of preparation 7, 102 91 PBu-5-Me-5-NB Example 8Polymer of preparation 8, 103 90 PAcNB

TABLE 2 n(refractive polymer index) (n_(x) − n_(y)) × 10³ R_(th)(nm/μm)(n_(y) − n_(z)) × 10³ Example 1 Polymer of 1.52 0.02 5.69 5.69preparation 1 Example 2 Polymer of 1.50 0.03 2.11 2.11 preparation 2Example 3 Polymer of 1.51 0.02 3.12 3.12 preparation 3 Example 4 Polymerof 1.51 0.02 3.38 3.38 preparation 4 Example 5 Polymer of 1.52 0.03 4.154.15 preparation 5 Example 6 Polymer of 1.52 0.03 3.43 3.43 preparation6 Example 7 Polymer of 1.51 0.02 3.78 3.78 preparation 7 Example 8Polymer of 1.52 0.02 5.45 5.45 preparation 8

And, when R_(θ) of the film was measured while overlapped with TAC filmsatisfying n_(y)>n_(z), R_(θ) of all the cyclic olefin-based filmsincreased, indicating that R_(th) of cyclic olefin-based film isattributable to negative birefringence (n_(y)>n_(z)) toward thicknessdirection. R_(θ) of the transparent films obtained in Examples 2˜7 atdifferent wavelengts (λ=479.4 nm, 548 nm, 629 m, 747.7 nm) were measuredusing an automatic double refractometer (Wangja measuring machine,KOBRA-21, ADH) at an incident angle of 50°. And, R₅₀(λ)/R₅₀(λ₀), a ratioto R_(θ) at a standard wavelength (λ₀=550 nm) was calculated and shownin Table 3. TABLE 3 R₅₀(479.4)/ R₅₀(548)/ R₅₀(629)/ R₅₀(747.7)/ PolymerR₅₀(λo) R₅₀(λo) R₅₀(λo) R₅₀(λo) Film of Polymer of 1.007 1.000 0.9980.987 example 2 preparation 2, PBeNB Film of Polymer of 1.007 1.0001.000 0.983 example 3 preparation 3, PBe-7-Me-3-NB Film of Polymer of1.010 1.000 0.997 0.965 example 4 preparation 4, PBe-5-Me-5-NB Film ofPolymer of 1.008 1.000 1.000 0.992 example 5 preparation 5,PBe-3-Me-7-NB Film of Polymer of 1.007 1.000 0.997 0.968 example 6preparation 6, PBu-7-Me-3-NB Film of Polymer of 1.010 1.000 0.993 0.972example 7 preparation 7, PBu-5-Me-5-NB

Examples 9˜11

(Preparation of Unified Polarizing Plate)

On one side of a polarizing film wherein iodine was dyed and oriented onPVA, TAC with a thickness of 80 μm which was surface treated with NaOHwas laminated using a PVA aqueous adhesive (3 wt %). Then, one surfaceof the cyclic olefin-based negative C-plate compensation/protectionlayer prepared in Examples 2 to 4 was corona discharge treated, and thetreated surface side was coated with PVA aqueous adhesive using a Graviaroll coater, and then, laminated to the other side of the polarizingfilm using a lamination roll, dried at 80° C. for 8 minutes to preparean oval unified polarizing plate. Corona discharge speed was 2 m/min,treated amount was 0.4 KV·A·min/m², and corona discharge frequency was˜10 KHz, and the distance between an electrode and film was 1.8 mm.

On the non-treated surface of the compensation/protection film of theprepared unified polarizing plate, acrylic adhesive was coated to athickness of about 30 μm, and adhered perpendicular to a glass plate of1.2 mm thickness with a size of 40×40 mm. Then, polarizing degree andlight permeability at 400˜700 nm of the center were measured, and hightemperature and high humidity test was carried out at 60° C., 90% RHrelative humidity, for 500 hours, and then, changes in lightpermeability and polarizing degree at center were measured and shown inTable 4.

The unified polarizing plate treated at high temperature high humiditydid not show exfoliation, spot, bubbles, or wrinkles. And, the unifiedpolarizing plate showed comparatively small change in birefringenceafter high temperature high humidity test, and thus non-uniformityaccording to the location of the sample was little, observed from thefront. TABLE 4 60° C., 90% RH, Initial value after 500 hours LightPolarizing Light Polarizing Protection compensation transmittance degreetransmittance degree layer (%) (%) (%) (%) Example 9 Film of Example 2,43.50 99.92 43.51 99.88 PBeNB Example 10 Film of example 3, 43.42 99.9243.44 99.89 PBe-7-Me-3 NB Example 11 Film of Example 4, 43.44 99.9143.45 99.89 PBe-5-Me-5 NB

Comparative Example 1

On one side of the same polarizing film as used in Examples 9 to 11, asurface-treated side of a TAC protection film with a thickness of 80 μmwhich is surface treated with NaOH solution was laminated using a PVAaqueous adhesive (3 wt %), and on the other side of the polarizing film,the TAC protection film was laminated in the same manner. The laminatedfilm was dried at 80° C. for 8 minutes to obtain a polarizing plate.

The same acrylic adhesive as used in Examples 9 to 11 was coated on aTAC protection film with a thickness of 30 μm, and adhered perpendicularto a glass plate with a thickness of 1.2 mm to a size of 40×40 mm. Lighttransmittance and polarizing degree at the center were respectively43.43% and 99.92%. High temperature high humidity test was carried outat 60° C., 90% RH relative humidity, for 500 hours, and lighttransmittance and polarizing degree were respectively measured to be43.50% and 99.75%. After the high temperature high humidity test, badappearance like bubbles, spot, and exfoliation can be observed in somepart (especially in edge part) of the sample. In addition to the badappearance, the sample shows relatively high non-uniformity in color dueto the local retardation difference.

According to the unified polarizing plate of the present invention, aconventional process, for optical compensation toward thicknessdirection, of coating an organic substance such as discotic liquidcrystal on a protection layer of a polarizing plate is not required, anda negative C-plate type optical anisotropic compensation/protectionfilm, which can control refractive index toward thickness directionaccording to the kinds and contents of functional groups introduced intocyclic olefin-based addition polymer, is adhered on at least one side ofa polarizing film. Thus, the unified polarizing plate of the presentinvention has superior durability at high temperature high humiditycompared to a polarizing plate employing TAC as a protection layer, andoffers improved wide view angle to a liquid crystal display havingpositive refractive index toward thickness direction when liquid crystaldisplay device is ON or OFF.

1. A polarizing plate comprising: a) a polarizing film; and b) aprotection layer of a transparent film comprising a cyclic olefin-basedaddition polymer.
 2. The polarizing plate according to claim 1, whereinthe transparent film is of negative C-plate type.
 3. The polarizingplate according claim 1, wherein the transparent film is laminated onone side of the polarizing film.
 4. The polarizing plate according toclaim 1, wherein the transparent film is laminated on both sides of thepolarizing film.
 5. The polarizing plate according to claim 1, whereinthe transparent film has retardation value (R_(th)) of 60 to 1000 nm,calculated by the following equation, when the thickness of thetransparent film is set to 30 to 200 μm:R _(th)=Δ(n _(y) −n _(z))×d wherein, n_(y) is a refractive index ofin-plane fast axis, measured at a wavelength of 550 nm, n_(z) is arefractive index toward thickness direction, measured at a wavelength of550 nm, and d is a thickness of the film.
 6. The polarizing plateaccording to claim 1, wherein the cyclic olefin-based addition polymeris i) a homopolymer of the compound represented by the followingChemical Formula 1; or ii) a copolymer of two or more kinds of thecompounds represented by the following Chemical Formula 1:

wherein m is an integer of 0 to 4, R₁, R₂, R₃, and R₄ are independentlyor simultaneously, a hydrogen; halogen; straight or branched alkyl,alkenyl or vinyl having 1 to 20 carbon atoms; cycloalkyl having 4 to 12carbon atoms, substituted or unsubstituted with hydrocarbon; aryl having6 to 40 carbon atoms, substituted or unsubstituted with hydrocarbon;aralkyl having 7 to 15 carbon atoms, substituted or unsubstituted withhydrocarbon; alkynyl having 3 to 20 carbon atoms; or a polar functionalgroup selected from the group consisting of linear or branchedhaloalkyl, haloalkenyl or halovinyl having 1 to 20 carbon atoms;halocycloalkyl having 4 to 12 carbon atoms, substituted or unsubstitutedwith hydrocarbon; haloaryl having 6 to 40 carbon atoms, substituted orunsubstituted with hydrocarbon; haloaralkyl having 7 to 15 carbon atoms,substituted or unsubstituted with hydrocarbon; haloalkynyl having 3 to20 carbon atoms; and non-hydrocarbonaceous polar group comprising atleast one of oxygen, nitrogen, phosphor, sulfur, silicon, or boron, whenR₁, R₂, R₃ and R₄ are not hydrogen, halogen or polar functional group,R₁ and R₂ or R₃ and R₄ may be connected with each other to form analkylidene group having 1 to 10 carbon atoms, or R₁ or R₂ may beconnected with one of R₃ and R₄ to form a saturated or unsaturatedcyclic group having 4 to 12 carbon atoms, or aromatic cyclic compoundhaving 6 to 24 carbon atoms.
 7. The polarizing plate according to claim6, wherein the non-hydrocarbonaceous polar group of the Chemical Formula1 is selected from the group consisting of: —C(O)OR₆, —R₅C(O)O₆, —OR₆,—R₅₀R₆, —OC(O)OR₆, —R₅OC(O)OR₆, —C(O)R₆, —R₅C(O)R₆, —OC(O)R₆,—R₅OC(O)R₆, —(R₅₀)_(p)—OR₆, —(OR₅)_(p)—OR₆, —C(O)—O—C(O)R₆,—R₅C(O)—O—C(O)R₆, —SR₆, —R₅SR₆, —SSR₆, —R₅SSR₆, —S(═O)R₆, —R₅S(═O)R₆,—R₅C(═S)R₆, —R₅C(═S)SR₆, —R₅SO₃R₆, —SO₃R₆, —R₅N═C═S, —NCO, R₅—NCO, —CN,—R₅CN, —NNC(═S)R₆, —R₅NNC(═S)R₆, —NO₂, —R₅NO₂,

wherein each R₅ is a linear or branched alkyl, haloalkyl, alkenyl,haloalkenyl, vinyl, halovinyl having 1 to 20 carbon atoms; cycloalkyl orhalocycloalkyl having 4 to 12 carbon atoms, substituted or unsubstitutedwith hydrocarbon; aryl or haloaryl having 6 to 40 carbon atoms,substituted or unsubstituted with hydrocarbon; aralkyl or haloaralkylhaving 7 to 15 carbon atoms, substituted or unsubstituted withhydrocarbon; or, alkynyl or haloalkynyl having 3 to 20 carbon atoms,each of R₆, R₇ and R₈ is a hydrogen; halogen; linear or branched alkyl,haloalkyl, alkenyl, haloalkenyl, vinyl, halovinyl, alkoxy, haloalkoxy,carbonyloxy, halocarbonyloxy having 1 to 20 carbon atoms; cycloalkyl orhalocycloalkyl having 4 to 12 carbon atoms, substituted or unsubstitutedwith hydrocarbon; aryl, haloaryl, aryloxy, or haloaryloxy having 6 to 40carbon atoms, substituted or unsubstituted with hydrocarbon; aralkyl orhaloaralkyl having 7 to 15 carbon atoms, substituted or unsubstitutedwith hydrocarbon; alkynyl or haloalkynyl having 3 to 20 carbon atoms,and p is an integer of 1 to
 10. 8. The polarizing plate according toclaim 1, wherein the cyclic olefin-based addition polymer comprisesnon-polar functional group.
 9. The polarizing plate according to claim1, wherein the cyclic olefin-based addition polymer comprises a polarfunctional group.
 10. The polarizing plate according to claim 1, whereinthe cyclic olefin-based addition polymer is a homopolymer ofnorbornene-based monomers comprising polar functional group, or acopolymer of norbornene-based monomers comprising different polarfunctional groups.
 11. The polarizing plate according to claim 1,wherein the cyclic olefin addition polymer is a copolymer ofnorbornene-based monomers comprising non-polar functional group andnorbornene-based monomers comprising polar functional group.
 12. Thepolarizing plate according to claim 1, wherein the transparent filmcomprises a blend of one or more kinds of cyclic olefin-based additionpolymers. 13, The polarizing plate according to claim 1, wherein thecyclic olefin-based addition polymer is prepared by a method comprisingaddition polymerizing norbornene-based monomers in the presence of Group10 transition metal catalyst.
 14. The polarizing plate according toclaim 1, wherein the cyclic olefin-based addition polymer is prepared bya method which comprise contacting norbornene-based monomers comprisingpolar functional group with a catalyst component of a catalyst systemcomprising: i) a catalyst component of Group 10 transition metalcompound; ii) a cocatalyst component of an organic compound thatcomprises Group 15 element and has noncovalent electron pair capable offunctioning as an electron donor; and iii) a cocatalyst component of asalt comprising Group 13 element capable of offering an anion that canbe weakly coordinated to the transition metal to effect additionpolymerization.
 15. The polarizing plate according to claim 1, whereinthe polarizing plate comprises a transparent optical film prepared fromcyclic olefin-based addition polymer comprising polar functional groupof ester or acetyl group, which is prepared by a method comprisingcontacting norbornene-based monomers comprising a polar functional groupof ester or acetyl group with a catalyst component of a catalyst systemcomprising: i) Group 10 transition metal compound; ii) a compoundcomprising a neutral Group 15 electron donor ligand having a cone angleof at least 160°; and iii) a salt capable of offering an anion that canbe weakly coordinated to the i) transition metal to effect additionpolymerization.
 16. The polarizing plate according to claim 1, whereinthe transparent film is prepared by a solution casting which comprisesthe step of dissolving cyclic olefin-based addition polymer in a solventand casting the solution into film.
 17. The polarizing plate accordingto claim 1, wherein one or more kinds of surface treatments selectedfrom the group consisting of corona discharge, glow discharge, flamtreatment, acid treatment, alkali treatment, UV irradiation, and coatingare conducted on the transparent film.
 18. A unified polarizing platecomprising an optically anisotropic transparent film laminated on atleast one side of a polarizing film, said optically anisotropictransparent film has retardation value (R_(th)) of 60 to 1000 nm,calculated by the following equation 1, phase difference ratio(R₄₅₀/R₅₅₀) of 1 to 1.05 and (R₆₅₀/R₅₅₀) of 0.95 to 1 (wherein R₄₅₀ isphase difference value at a wavelength of 450 nm, R₅₅₀ is a phasedifference value at a wavelength of 550 nm, and R₆₅₀ is a phasedifference value at a wavelength of 650 nm):R _(th)=Δ(n _(y) −n ₂)×d  [Eqation 1]wherein, n_(y) is a refractiveindex of in-plane fast axis, measured at a wavelength of 550 nm, n_(z)is a refractive index toward thickness direction, measured at awavelength of 550 nm, and d is a thickness of a film.
 19. The unifiedpolarizing plate according to claim 18, wherein the opticallyanisotropic transparent film has light transmittance of at least 90% ata wavelength of 400 to 800 nm.
 20. The unified polarizing plateaccording to claim 18, wherein the optically anisotropic transparentfilm comprises cyclic olefin-based addition polymer.
 21. The unifiedpolarizing plate according to claim 18, wherein the opticallyanisotropic transparent film has retardation value (R_(th)) of 60 to1000 nm, calculated by the following equation 1, when the thickness ofthe optically anisotropic transparent film is set to 30 to 200 μm:R _(th)=Δ(n _(y) −n _(z))×d  [Equation 1]wherein n_(y) is a refractiveindex of in-plane fast axis, measured at a wavelength of 550 nm, n_(z)is a refractive index toward thickness direction, measured at awavelength of 550 nm, and d is a thickness of the film.
 22. The unifiedpolarizing plate according to claim 18, wherein the opticallyanisotropic film has refractive index satisfying n_(x)≅n_(y)>n_(z)(wherein n_(x) is refractive index of in-plane slow axis, n_(y) isrefractive index of fast axis, and n_(z) is refractive index towardthickness direction).
 23. The unified polarizing plate according toclaim 18, wherein the polarizing plate simultaneously performs functionsas a negative C-plate for optical compensation and as a polarizingplate.
 24. A method for preparing a polarizing plate having negativerefractive index toward thickness direction, comprising the steps of: a)conducting addition polymerization of norbornene-based monomers toprepare a norbornene-based addition polymer; b) dissolving thenorbornene-based addition polymer in a solvent to prepare anorbornene-based addition polymer solution; c) coating or casting thenorbornene-based addition polymer solution on a hard surface and drying;and d) laminating the cast film on a polarizing film.
 25. The methodaccording to claim 24, wherein the lamination in the step d) isconducted after conducting surface treatment of the cast film selectedfrom the group consisting of corona discharge, glow discharge, flametreatment, acid treatment, alkali treatment, UV irradiation and coating.26. The method for preparing a polarizing plate according to claim 24,wherein the polarizing plate comprises a protection layer placed on oneside or both sides of the polarizing film.
 27. A liquid crystal displaycomprising the polarizing plate described in claim
 1. 28. The liquidcrystal display according to claim 27, wherein the liquid crystaldisplay comprises liquid crystal cell mode, of which liquid crystallayer has refractive index satisfying n_(x)≅n_(y)<n_(z), when power ofliquid crystal display device is ON or OFF (wherein n_(x) is refractiveindex of in-plane slow axis, n_(y) is refractive index of in-plane fastaxis, and n_(z) is refractive index toward thickness direction).